• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.8
• /
• pp.1083-1089
• /
• 2010

Shape memory alloys (SMAs) are smart materials. The unique characteristics of SMAs enable the production of large force and displacement. Hence, SMAs can be used in many applications such as in actuators and active structural acoustic controllers; the SMAs can also be used for dynamic tuning and shape control. A SMA torque tube actuator consisting of SMA tubes and superelastic springs is proposed, and the behaviors of the actuator are investigated. From the results of heat transfer analysis, it is proved that the SMA torque tube actuator with both resistive heating of SMA itself and a separate conventional heating rod in the tube core has good performance. The behavior of an actuator system was analyzed by performing a contact analysis, and the twisting motion was noticed when checking the actuation. 3D SMA nonlinear constitutive equations were formulated numerically and implemented by performing a nonlinear analysis by using Abaqus UMAT.

• Steel and Composite Structures
• /
• v.33 no.6
• /
• pp.823-836
• /
• 2019

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiral-welded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'_c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

• Journal of the Korea Concrete Institute
• /
• v.26 no.6
• /
• pp.707-714
• /
• 2014

CFT (Concrete-Filled Tube) is a type of steel column comprised of steel tube and concrete. Steel tube holds concrete and the concrete inside tube takes charge of compressive load. This study presents structural performance of the CFT column which has 73~100 MPa high strength concrete inside. Fluidity, mechanical compression, pump pressure test in flexible pipe were conducted for understanding properties of the high strength concrete. Material properties were achieved by various experimental tests, such as slump, slump flow, air content, U-box, O-Lot, L-flow. In addition, mock-up tests were conducted to monitor concrete filling, hydration heat, compressive strength. From construction sites in Sang-am dong and University of Seo-kang, long-term behaviors could be effectively predicted in terms of ACI 209 material model considering elastic deformation, shrinkage and creep.

• Korean journal of applied entomology
• /
• v.55 no.3
• /
• pp.223-233
• /
• 2016

In order to identify a new control measure for a sporadic insect pest, Pochazia shantungensis, 23 types of essential oils were screened for their repellent effects, with an olfactory test using a Y-tube olfactometer. Results indicated that 21 essential oils, except lemongrass oil and peppermint oil, did not show repellent activity against P. shantungensis. The repellent effect of peppermint oil was over 80%. When 0.1, 0.5, and $1{\mu}l$ of peppermint oil were used, the rate of repelling of P. shantungensis gradually increased, and was as high as 76.5% when $10{\mu}l$ was used. The main components of peppermint oil were 1,8-cineole, iso-menthyl acetate, menthone, and menthol, at 4.7, 8.0, 23.8 and 53.7%, respectively. When the three main components were mixed using a Y-tube olfactometer, a strong repellent effect (76.2%) was observed when $5{\mu}l$ was used. Peppermint oil showed a repellent and ovipositional repellent effect against P. shantungensis in the field. However, this activity persists only for a short period, and high concentrations can lead to phytotoxicity. Therefore, it is necessary to develop ideal formulations.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.11 no.3
• /
• pp.241-248
• /
• 2001

The main factors of breakthrough are known to sampling time, flow rate, concentration of the sample, temperature, humidity, and the physical characteristics of the solid sorbent tube. However, no study has been reported the effect of temperature and sampling volume on the breakthrough of acharcoal tube during vinyl chloride monomer (VCM) sampling. The objective of this study is to suggest the optimal sampling condition during VCM sampling based on National Institute for Occupational Safety and Health (NIOSH) method. To evaluate adequate sampling volume for VCM without breakthrough, volume of 1, 2, 3, 4, and 5 L each from VCM of 1, 5, 10, 15, and 20ppm at flow rate of 0.05 L/min were sampled in $22^{\circ}C$ and $40^{\circ}C$. At $22^{\circ}C$, in the case of 1, 5, 10, and 15ppm, VCM was adsorbed completely in first section of charcoal tube regardless of sampling volume. But in 20ppm, detection rates are 99.56% in first section and 0.44% in second section. At $40^{\circ}C$ of 1ppm, VCM was adsorbed completely in first section. In 10, 15, and 20ppm, detection rates of second, third, and forth sections were decreased significantly by reduction of sampling volume. In determination of breakthrough based on NIOSH method, no breakthrough was occurred in 20ppm at $22^{\circ}C$. At $40^{\circ}C$, breakthrough was occurred in 10, 15, and 20ppm when sampling volume was 5L. Although no breakthrough was occurred when sampling volume was 3L. Finally, in environment of temperature around $22^{\circ}C$, breakthrough may not occurred up to 20ppm during sampling for VCM. During sampling for VCM in environment of temperature around $40^{\circ}C$, no breakthrough occurred in 1-5ppm and 10-20ppm when sampling volume is 5L and 3L respectively. This result suggests that the sampling volume should be considered when VCM sampling under hot conditions (> $22^{\circ}C$) by the NIOSH method No. 1007.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.138-152
• /
• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.5
• /
• pp.515-522
• /
• 2010

The objective of this study is to investigate the air-side heat transfer characteristics of a spirally-coiled circular fin-tube heat exchanger for various geometric parameters under non-frosting conditions. The heat transfer characteristics of the heat exchanger were analyzed with respect to heat exchanger geometries, and then, the characteristics were compared with those of rectangular-plate fin-tube heat exchangers with discrete fins. The heat transfer coefficient increased with a decrease in the number of tube rows and an increase in the fin pitch. The optimum length of the L-foot was 2.7 mm. In addition, the heat transfer rate increased with a decrease in the tube pitch and the tube thickness. The heat transfer coefficient of the spirally-coiled circular fin-tube heat exchanger was 24.3% higher than that of the rectangular-plate fin-tube heat exchanger.

• Analytical Science and Technology
• /
• v.23 no.1
• /
• pp.45-53
• /
• 2010

For the determination of chlorine in uranium compound, analytical methods by using a steam distillation and a pyrohydrolysis have been developed. The steam distillation apparatus was composed of steam generator, distilling flask and condenser etc. The samples were prepared with an aliquot of LiCl standard solution and a simulated spent nuclear fuel. A sample aliquot was mixed with a solution containing 0.2 M ferrous ammonium sulfate-0.5 M sulfamic acid 3 mL, phosphoric acid 6 mL and sulfuric acid 15 mL. The chloride was then distilled by steam at the temperature of $140^{\circ}C$ until a volume of $90{\pm}5\;mL$ is collected. The pyrohydrolysis equipment was composed of air introduction system, water supply, quartz reaction tube, combustion tube furnace, combustion boat and absorption vessel. The chloride was separated from powdered sample which is added with $U_3O_8$ accelerator, by pyrohydrolysis at the temperature of $950^{\circ}C$ for 1 hour in a quartz tube with a stream of air of 1 mL/min supplied from the water reservoir at $80^{\circ}C$. The chlorides collected in each absorption solution by two methods was diluted to 100 mL and measured with ion chromatography to determine the recovery yield. For the ion chromatographic determination of chlorine in molten salt retained in a metal ingot, the chlorine was separated by means of pyrohydrolysis after air and dry oxidation, and grinding for the sample.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.09b
• /
• pp.1118-1119
• /
• 2005

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.09b
• /
• pp.1068-1069
• /
• 2005